Cancer is the second leading cause of death in postmenopausal women. Therefore, detailed investigations are warranted to identify potentially modifiable risk factors for cancer. This project will characterize the relationship between topographical distribution of body fat and risks of endometrial cancer, breast cancer, and total mortality in postmenopausal women. The project has two components. In a longitudinal cohort study 25,000 Iowa women ages 55-69 years will be recruited by mail. Subjects will complete a questionnaire on cancer risk and perform self-measurements of body weight, height, and girths. The cohort will be followed four years for incidence rates of endometrial cancer, breast cancer, and total mortality. Incidence will be ascertained via the Iowa Cancer Surveillance Epidemiology and End Results (SEER) program, and mortality, via the National Death Index. It is hypothesized that those with "upper body" fat predominance (high ratios of waist to hip girths) will have higher incidences of study endpoints than those with "lower body" fat predominance (low waist to hip girth ratios). A cross-sectional study will also be performed comparing serum levels of estrone, estradiol, testosterone, androstenedione, and sex hormone binding globulin (SHBG) in 25 postmenopausal women with obesity and "upper body" fat predominance versus 25 with obesity and "lower body" fat predominance versus 25 nonobese controls. It is hypothesized that the obese women will have higher serum levels of free estrone, free estradiol, free testosterone, and androstenedione, and lower levels of SHBG than nonobese women, but those with "upper body" fat predominance will have more extreme hormone levels than those with "lower body" fat predominance. The proposed project, therefore, will provide new information on the relationship between body fat distribution and cancer risk. This information could be valuable in the primary prevention of disease in women.